1. Field of the Invention
The present invention relates to the generation of positioning commands for controlling motors, such as servo motors, and particularly to a positioning apparatus for exercising synchronous control with only the motors, without employing actual machine mechanisms, such as connecting shafts, clutches, gears and cams.
2. Description of the Background Art
It is known in the art that there are industrial machines consisting of a large number of movable parts which must operate synchronously with each other.
A first conventional embodiment will be described in reference to the appended drawings. FIG. 121 illustrates the arrangement of a fluid filling machine as an example of a machine described above, of which numerous movable parts operate synchronously with each other. Referring to FIG. 121, the numeral 400 indicates a motor, 401 a connecting shaft, 402a, 402b, 402c and 402d gears, 403a, 403b and 403c clutches, 404 a transfer shaft, 405 a lifting shaft, 406 a filling shaft, 407 a conveyor, 408 a transferring cam, 409 a lifting cam, 410 a filling cam, 411 a lifting table, 412 a vessel filled with liquid, 413 a filling cylinder, 414 a filling piston, and 415 a filling nozzle.
FIGS. 122A-122C show the operations of the conveyor 407, lifting table 411 and filling piston 414 illustrated in FIG. 121, wherein a horizontal axis indicates time and a vertical axis denotes the velocities of the conveyor 407, lifting table 411 and filling piston 414.
In FIGS. 122A-122C, the velocities of the conveyor 407, lifting table 411 and filling piston 414 are determined in accordance with the patterns of the transferring cam 408, lifting cam 409 and filling cam 410 in FIG. 121.
The operation of the machine in FIG. 121 will now be described. The motor 400 not only provides power to the whole filling machine but also rotates the connecting shaft 401 to synchronize the whole filling machine. The connecting shaft 401 transmits the motion of the motor 400 via the gears 402a-402d to the transfer shaft 404, lifting shaft 405 and filling shaft 406. The transfer shaft 404 is connected to the conveyor 407 to transfer the vessel 412 filled with liquid. The lifting shaft 405 is connected to the lifting table 411 which is risen up to the position of a fill hole for filling the vessel 412 with liquid and is lowered as the vessel 412 is filled with liquid, and the filling shaft 406 is built to operate the filling piston 414 for sucking the liquid into the cylinder 413, discharging the liquid from the cylinder 413, and filling the vessel 412. The clutches 403a to 403c are engaged when the rotation of the connecting shaft 401 is transmitted to each of the transfer shaft 404, lifting shaft 405 and filling shaft 406, and are disengaged when the rotation is not transmitted.
Referring to FIG. 121, all the clutches 403a to 403c are first disengaged, the clutches of the transfer shaft 404, lifting shaft 405 and filling shaft 406 are then engaged separately on a shaft-by-shaft basis, and the shafts are operated to move the conveyor 407, lifting table 411 and filling piston 414 to their initial positions. All the clutches 403a to 403c are then engaged at the same time, and the transfer shaft 404 is operated in accordance with the motion of the motor 400 and the pattern of the transferring cam 408, thereby operating the conveyor 407. At this time, as shown in FIG. 122C, the filling piston 414 simultaneously performs suction operation in accordance with the pattern of the filling cam 410 (Interval A in FIG. 122C). After the conveyor 407 has reached a predetermined place, the lifting table 411 rises in accordance with the pattern of the lifting cam 409, moving the vessel 412 to be filled with liquid up to a predetermined height (interval B in FIG. 122C). The lifting table 411 is then lowered in accordance with the pattern of the lifting cam 409, and the filling piston 414 concurrently performs filling operation in accordance with the pattern of the filling cam 410 (interval C in FIG. 122C). By thus transmitting the motion of the motor 400 via the connecting shaft 401 to the transfer shaft 404, lifting shaft 405 and filling shaft 406, the sequence of operations are performed in synchronization with the motion of the motor 400.
A second conventional embodiment will now be described with reference to the appended drawings. FIG. 123 shows a conventional embodiment employing a single positioning controller to control transfer, lifting and filling operations with servo motors, wherein 421 indicates a transferring servo motor, 422 a lifting servo motor, 423 a filling servo motor, 424 a servo amplifier for controlling the transferring servo motor 421, 425 a servo amplifier for controlling the lifting servo motor 422, 426 a servo amplifier for controlling the filling servo motor 423, and 420 a positioning controller for giving position commands to the servo amplifiers 424 to 426, and 427 is equivalent to a transfer apparatus including the transfer shaft 404 and conveyor 407 in FIG. 121, 428 equivalent to a lifting apparatus including the lifting shaft 405 and lifting table 411 in FIG. 121, and 429 equivalent to a filling apparatus including the filling shaft 406, filling cylinder 413, filling piston 414 and filling nozzle 415 in FIG. 121.
The operation of the second conventional embodiment will now be described in reference to FIG. 123. The positioning controller 420 gives position commands to the servo amplifiers 424-426 in accordance with a positioning program which causes the conveyor, lifting table and filling piston to operate as shown in FIGS. 122A-122C. The positioning program is written to perform the two-axis interpolative operation of the transfer shaft 404 and filling shaft 406 in the interval A in FIGS. 122A-122C, so that the transferring servo motor 421 is rotated to operate the conveyor 407 and locate the vessel 412 to a liquid filling position, and also the filling servo motor 423 is rotated to lower the filling piston 414 and fill the filling cylinder 413 with liquid. Then, in the interval B in FIGS. 122A-122C, the program is written to rotate the lifting servo motor 422 to raise the lifting table 411. Finally, in the interval C in FIGS. 122A-122C, the program is written to perform the two-axis interpolative operation of the filling shaft 406 and lifting shaft 405 so that the filling servo motor 423 is rotated to raise the filling piston 414 and fill the vessel 412 with the liquid from inside the filling cylinder 413, and simultaneously, the lifting servo motor 422 is rotated to lower the lifting table 411.
A third conventional embodiment will now be described with reference to the appended drawings. FIG. 124 shows the third conventional embodiment using three servo amplifiers having a single-axis positioning function with the transfer shaft 404, lifting shaft 405 and filling shaft 406 for operating them in accordance with commands from a single sequence controller. 421 to 423, 427 to 429 and 431 to 433 indicate parts identical to those shown in FIG. 123.
The operation of the third conventional embodiment will now be described with reference to FIG. 124. When provided with an operation command 1, the transferring servo amplifier 431 rotates the transferring servo motor 421 to operate the conveyor 407 in a pattern indicated in the interval A in FIG. 122A. When given an operation command 2, the lifting servo amplifier 432 rotates the lifting servo motor 422 to operate the lifting table 411 in a pattern indicated in the interval B in FIG. 122B, and when provided with an operation command 3, rotates the lifting servo motor 422 to operate the lifting table 411 in a pattern indicated in the interval C in FIG. 122B. When given an operation command 4, the filling servo amplifier 433 rotates the filling servo motor 423 to operate the filling piston 414 in a pattern indicated in the interval A in FIG. 122C, and when provided with an operation command 5, rotates the filling servo motor 423 to operate the filling piston 414 in a pattern indicated in the interval C in FIG. 122C.
The sequence controller 430 simultaneously provides the transferring servo amplifier 431 with the operation command 1 and the filling servo amplifier 433 with the operation command 4. After receiving completion signals indicating that respective operations are complete, the sequence controller 430 gives the lifting servo amplifier 432 the operation command 2. Thereafter, when receiving a completion signal indicating that the operation of the lifting table 411 is complete, the sequence controller 430 simultaneously issues the operation command 3 to the lifting servo amplifier 432 and the operation command 5 to the filling servo amplifiers 433, thereby operating the conveyor 407 and filling piston 414. The sequence controller 430 thus communicates the operation commands and completion signals with the transferring servo amplifier 431, lifting servo amplifier 432 and filling servo amplifier 433 to operate the conveyor 407, lifting table 411 and filling piston 414 in the patterns shown in FIGS. 122A-122C.
A fourth conventional embodiment will now be described with reference to FIG. 125 which shows an example of a conveyor line where products transferred on a belt conveyor are machined in sequence by a plurality of machines to finish them into end products. 444 indicates a belt conveyor, 443a and 443b objects to be machined which are transferred on the belt conveyor, 442a and 442b rollers supporting the belt conveyor, 440 an induction motor for driving the roller 442a via a gear 441, 445 an encoder mounted to the roller 442b for detecting the travel of the belt conveyor, 446a and 446b positioning controllers, 447a and 447b encoder input interfaces provided inside the positioning controllers 446a and 446b, respectively, and 448a and 448b objects to be controlled incorporating servo motors, such as robots or machines, controlled by the commands of the positioning controllers 446a and 447b, respectively.
The operation of the fourth conventional embodiment will now be described. The induction motor 440 keeps running at a constant velocity, rotating the roller 442 via the gear 441. The rotation of this roller 442a drives the belt conveyor 444, transferring the objects to be machined 443a, 443b. The objects to be controlled 448a, 448b, which are machines containing servo motors for machining the objects to be machined 443a, 443b, operate in accordance with the commands of the positioning controllers 446a, 446b written as positioning programs for machining operations to be performed when the belt conveyor 444 is at a stop. The positioning controllers 446a, 446b have different positioning programs according to the conveyor line, and the objects to be controlled 448a, 448b may either be identical or different.
When the objects to be machined 443a, 443b are at a stop, they can be machined by the above operations. When the belt conveyor 444 is in motion, however, machining must be carried out in synchronization with the motion of the belt conveyor 444. For this purpose, the travel of the belt conveyor 444 is detected from the encoder 445 and fetched into the controllers 446a, 446b via the encoder input interfaces 447a, 447b. Each of the positioning controllers 446a, 446b contains firmware which composes the fetched travel of the belt conveyor 444 and the travel of positioning operation by the positioning program. The results composed by the firmware are given to the objects to be controlled 448a, 448b as commands. This allows the objects to be machined 443a, 443b to be machined in synchronization with the motion of the belt conveyor 444 by only writing positioning programs for machining with the belt conveyor 444 at a stop, whereby machining time can be reduced as compared to machining performed after stopping the belt conveyor 444.
A fifth conventional embodiment will now be described in reference to the appended drawings. FIG. 126 is an arrangement diagram showing tension control by a dancer roll known in the art, wherein 190 indicates a hold-down roller for roll #1, 191 a roll #1, 192 a motor #1 for rotating the roll #1, 193 a servo amplifier #1 for controlling the motor #1, 195 a dancer roll, 194 and 196 rollers, 200 a hold-down roller for roll #2, 201 a roll #2, 202 a motor #2 for rotating the roll #2, 203 a servo amplifier #2 for controlling the motor #2, 198 a displacement detector for converting a displacement value from the center position of the dancer roll 195 into an electrical signal, 197 a spring for providing the dancer roll 195 with predetermined force, 460 a velocity command given to the servo amplifiers #1 and #2, 461 a compensation velocity command output from the displacement detector 198, and 462 an interface for inputting the compensation velocity command 461.
The operation of the fifth conventional embodiment will now be described. When the velocity command 460 is given, both the rollers #1 and #2 run at identical speeds if the compensation velocity command 461 is zero. The speed of the roller #2 is controlled by the displacement detector 198 which outputs a positive compensation velocity command 461 as shown in FIG. 127 when the displacement of the dancer roll 195 is on the upper side, and outputs a negative compensation velocity command 461 as shown in FIG. 127 when the displacement of the dancer roll 195 is on the lower side. This controls the dancer roll 195 to be kept in the center of an allowable stroke.
A sixth conventional embodiment will now be described with reference to the appended drawings. FIG. 128 is an arrangement diagram showing differential gears known in the art, wherein 480 indicates an input axis, 481 a gear a rotated Jointly with the input axis 480, 483 a gear b revolving around the gear a 481 while simultaneously rotating on its own axis by the rotation of the gear a 481 and a gear d 484, 482 a gear c disposed on the opposite side of the gear b 483 relative to the center point of the gear a 481 and similar to the gear b 483, 484 a cylindrical gear d concentric with the gear a 481 and equipped with an internal gear and an external gear, 485 an output axis connecting the center points of the gears b and c 483 and 482, 487 an auxiliary input axis for rotating a gear e 488, 488 a gear e rotated Jointly with the auxiliary input axis 487, 486 a cam rotated by the output axis 485, and 489 a load moved linearly by the rotation of the cam 486.
The operation of the sixth conventional embodiment will now be described. When the input axis 480 rotates, the gear a rotates in the same direction as the input axis 480. When the gear a rotates, the gears b and c rotate in the opposite direction. If the gear d is at rest at this time, the gears b and c revolve around the gear a in the same direction as the input axis 480, and the output axis 485 connecting the center points of the gears b and c rotates in the same direction similarly. The cam 486 connected with the output axis 485 also rotates in the same direction similarly. The load moves linearly in accordance with the shape of the cam 486. When the auxiliary input axis 487 rotates in the same direction as the input axis 480, the gear e rotates in the same direction as the auxiliary input axis 487. When the gear e rotates, the gear d rotates in the opposite direction. When the gear d rotates, the gears b and c rotate in the opposite direction and revolve around the gear a in the opposite direction to the auxiliary input axis 487, and the output axis 485 connecting the center points of the gears b and c rotates in the opposite direction similarly. Therefore, the output axis 485 is driven from both the input axis 480 and auxiliary input axis 487.
FIG. 129 shows the displacement curve of the cam 486, wherein one revolution of the output axis 485 is one cycle. Fundamentally, the cam 486 is rotated only by the input axis 480. When it is desired to adjust the phase of the cam 486 displacement curve, however, the auxiliary input axis 487 is rotated to turn the cam 486, thereby adjusting the starting position. This allows the phase of the cam 486 displacement curve to be adjusted without changing the rotational pattern of the input axis 480.
To rotate the cam 486 without turning the input axis 480 during adjustment, the auxiliary input axis 487 may only be rotated.
A seventh conventional embodiment will now be described in reference to the appended drawings. FIG. 130 indicates the settings of a positioning program consisting of a target position address, command velocity, and acceleration and deceleration times.
The operation of the seventh conventional embodiment will now be described. When positioning is started, a positioning pattern is calculated from the target position address, command velocities and acceleration and deceleration times, and is output to a servo amplifier in a pattern as shown in FIG. 131. Hence, the positioning pattern cannot be fine-adjusted.